1. Field of the Invention
The present invention involves methods of deterring illicit copying of electronically published documents by creating unique identification codes specific to each subscriber. Each copy of the published document has a unique arrangement of electronically created material, e.g. print material or display material, which is not quickly discernable to the untrained human eye. These unique identification codes discourage illicit copying and enable a publisher/copyright owner to analyze illicit copies to determine the source subscriber.
2. Detailed Background
When the quality of reproductions from copy machines became comparable with the original, the cost of copies was reduced to a few pennies per page, and the time it took to copy a page was reduced to a second or less, then copy machines started to present a threat to publishers. The problem is intensified in the electronic domain. The quality of a reproduction is identical with the original, there is almost no cost associated with making the copy, and with a single keystroke, hundreds of pages can be copied in a fraction of a second. In addition, electronic documents can be distributed to large groups, by electronic mail or network news services, with almost no effort on the part of the sender.
The ability to easily and inexpensively copy and distribute electronic documents is considered to be the main technical problem that must be overcome before electronic publishing can become a viable alternative to conventional publishing. Preventing an individual from duplicating a file of data that is in his possession is an extremely difficult, if not impossible task. Instead of trying to prevent duplication of general data files, the present invention is directed to making electronic publishing more acceptable by making it possible to identify the original owner of a bitmap version of the text portion of a document. With the current copyright laws, the present invention should be adequate to discourage much of the copying and distribution that might otherwise occur. An interesting result of the present invention method is that a publisher or copyright owner can also determine who the original belonged to when reproduced copies are found.